Biologist finds flexibility in nerve cell construction

COLUMBIA, Mo. – Since confirming the existence of ion channels in cells more than 30 years ago, countless scientists have attempted to find out exactly how these essential proteins operate. A new study by a University of Missouri-Columbia researcher is making the most complex and confounding organ in the body (the brain) a little less so, and may help uncover the unique set of rules that causes one type of nerve cell to perform its functions and another cell to perform an entirely different set of operations.

David J. Schulz, assistant professor, Biological Sciences, has helped develop an understanding of the fundamental mechanisms governing cell activity: that there is not a standard blueprint for how many ion channels one type of neuron needs to do its specific task, but rather there is more than one way to construct the same nerve cell. As a result, researchers are now one step closer to learning what defines particular types of nerve cells and what these cells try to do to compensate for when things go wrong.

“I would guess that most neuroscientists five or 10 years ago might say that if you see the same nerve cell doing the same thing in multiple people or animals, that would essentially be the result of their being built the same – that they have the same ion channel proteins and the same amounts of each protein,” Schulz said. “The work that we’re doing shows that you can get exactly the same output in these nerve cells, but the cells can be built differently. They can use different ion channels or different amounts of ion channels as long as these cells are doing the right thing, which is key for what the brain and the spinal cord need to accomplish. In a nutshell, a cell doesn’t really care how it accomplishes something as long as it does accomplish it.”

Schulz’s study, which took nearly two years to complete, appears in the July 25, 2007, issue of Proceedings of the National Academy of Sciences (PNAS) and is co-authored by Jean-Marc Goaillard and Eve Marder of Brandeis (Mass.) University. The researchers took individually identified nerve cells from multiple animals and measured the level of gene expression of multiple channels in the same cell. They found that the level of ion channels could vary quite a bit across the same cell types in different animals, but in different cell types there were unique clusters of ion channels that seemed to be correlated in their expression. This led them to conclude that while the same cell in different animals can vary considerably, there are some rules that tie together the same cell type and make them unique.

“If we understand the fundamental building blocks of how these cells are put together under normal conditions, then we have a much better chance of understanding what these cells do to cope with problems they encounter,” Schulz said. “For example, we’re starting to uncover some of the compensatory mechanisms of what happens when you remove input to cells, what these ion channels might do, and how they might be co-regulated and altered in order to increase or decrease the cell’s excitability. With these compensatory mechanisms could be implications for understanding spinal-cord injury or even epilepsy. The question we’re working on is a basic research question and not an injury model per se. But we hope that by looking at the normal function of nerve cells we might then provide insight as to what happens when things go wrong.”